WHY SPARE TIRES MIGHT SOON BE HISTORY
To the list of items you should no longer expect to see in a new car — those once-common features like a metal ignition key, an ashtray or a vent window that swings open — you may soon be adding the spare tire.
Already, nearly a third of the 2017 models offered in the United States do not come outfitted with a save-the-day spare as standard equipment, according to a recent study by AAA.
In truth, the extinction of the spare tire has been happening, if gradually, for years. Full-size spares gave way to the space-saving “doughnut” versions you sometimes spot on vehicles traveling at worrying speeds. They, in turn, are yielding their underfloor real estate to no tire at all.
The elimination of the spare by automakers is not entirely an abandonment of good sense or a severe example of cost-cutting; in fact, it can benefit drivers. The primary goal is weight reduction, a crucial factor in meeting fuel economy standards.
Removing a substantial amount of rubber and steel — up to 40 pounds, according to industry experts — along with a jack and a lug wrench is a big win for engineers who are conditioned to shave ounces wherever possible. But as appealing as it may be to skip the doughnut and lose a little weight, the disappearing spare can cause headaches: AAA said that last year it had answered roadside assistance calls from 450,000 members whose cars did not have spares — a situation that can mean a trip to the repair shop on a flatbed.
The freedom to eliminate spare tires altogether is largely possible as a result of developments in tire construction technology.
An increasingly popular alternative to spares is the so-called run-flat design, which most new BMW models use. Intended to make roadside tire changes unnecessary, this solution employs a reinforced tire sidewall that typically lets the driver continue for 50 miles at up to 50 mph after air pressure is lost. But they can be more costly: It may be necessary to replace, rather than simply patch, a damaged tire, and replacements are typically priced $25 to $50 higher than a conventional design.
Another alternative is the self-sealing tire, an older solution reappearing in modern form on the battery-powered Chevrolet Bolt, where reduced weight translates to more miles per charge. Designed solely as an electric vehicle, the Bolt has no provision for carrying a spare. According to Michelin, which supplies the Bolt’s Energy Saver A/S Selfseal rubber, the extra cost of a self-sealing tire — which can continue down the road even with a nail in the tread — is about $33 compared with conventional tires of the same size.
But some models are losing the spare without the benefit of runflat or self-sealing rubber, instead including conventional tires and a leak repair kit — packaged in an aerosol can or used in conjunction with a small air compressor powered by the car’s battery.
Such kits skim weight while skipping the tire, but have limited abilities to deal with any road hazard more serious than a nail hole in the tire’s tread section. A larger tear in the tire — something that can happen when modern low-profile tires meet a pothole — or damage to the sidewall or wheel rim will not be fixed by a leak kit. The sealants, which are usually one-time use devices, have a finite shelf life — usually from four to eight years, AAA said — and cost about $40 to replace.
The disappearance of the spare tire might be more than just an exercise in efficiency. It may be a sociological statement. A survey by AAA found that some 20 percent of drivers do not know how to change a flat tire, and with the rise of roadside assistance coverage for new cars, that number is unlikely to shrink.
A tire inflator that came standard with the 2011 Chevrolet Cruze Eco steps in for the spare tire that might otherwise have been used in this situation. A survey by AAA showed a third of 2017-model cars are not supplied with a spare tire.